Necro time... All of these variables don't change the fact that one driver is better equipped to operate with less distortion. You could argue that one woofer will produce 105 dB at some arbitrary frequency with 5% THD and another does the same with 7% THD. Yet the one with 7% at 105 dB produces 15% at 110 dB and the one that started at 5% is now up to 20%. Which one is better? Well sound level are you going after? What I'm assuming is that you've considered all other variables because those are unique to the install. You should not be considering an 18" sub if you're looking to add some low end to your stock system. In the same sense, you should not be looking to add an 8" sub if you're looking for the loudest sound you can get. Look up how to perform a proper scientific experiment. You must have your controls and ideally only one variable which you are going to study. In this case, if its a quality sub built for sound quality, you'll know based on design features such as the motor structure. And those things cost money and that production cost is passed onto the consumer. So really, considering most of these ID guys are selling at low profit margins (minus most of the "elite" sh*t) so you can safely assume you're getting what you pay for up until a certain point. The TC sounds LMS5400 is the undisputed lowest distortion woofer out there and I'm willing to bet it will sound better than any woofer you've heard. HOWEVER, in your install, if you fvck something up, the LMS could come out as sounding the poorest of the group. Taken out of the scenario, the LMS is still the best, but in your example, it may very well not have been. This typically implies something isn't quite right in your setup, but its your setup therefore it is designed to please you, NOT meet the idea of "sound quality". Thats another thing, sound quality in reality is entirely subjective. Look up the definition of "quality". quality from a scientific perspective is a feature that is not measurable in a meaningful manor because it is relative.

Ever heard both? One has an Xmax of 27.4 and the other of 22. In theory, the RL-P18 would be cleaner at 22 than the IXL at 22mm because one is reaching xmax whereas the other still has some way to go. I own an Rlp and have had an IXL for longer than they have been available for sale. So yes I have heard both, lol. Quoting an Xmax spec is not helping your argument. Not at all. Then what oh mighty god would quantify that the RL-P sounds cleaner? Oh right, thats entirely subjective and therefore cannot be compared anywhere at any time. Then how does the LMS sound so much cleaner than any other sub out there? Ikka's sub testing from the Home Theater Shack comes to mind... Which one sounds better to you then? Or is there no difference?

Are you new to modeling woofers though? Because that provides a direct comparison... Google WinIsd or Unibox. Also define, "basic". If you're talking about your standard Xplode or some cheap Best buy JBL then this 10 will rock your socks off!

Ever heard both? One has an Xmax of 27.4 and the other of 22. In theory, the RL-P18 would be cleaner at 22 than the IXL at 22mm because one is reaching xmax whereas the other still has some way to go. Not to be rude but this has what to do with the question at hand? I'm biased but I think the IXL is a great little sub, especially for the price. Jono I'm saying for the price, its great, and beats most store bought subs in higher price ranges but there is better out there.

It all depends on your listening habits... if you like it loud, closer to 1000 watts might be a better idea. If you like it moderate, a couple hundred watts would be fine. Actual dB levels would be most helpful in determining how much is enough.

This works well... Can't say much for in car but I've been running this as a computer sub for a while now and its simply amazing. 220 L box with two 1600 g 18" PR's from CSS powered by an EP-1500 which is good for 1200 watts at 4 ohms (tested wattage). As a side note, a SSF might be a good idea.

As far as SQ goes, a SS RL-P18 is a better sounding woofer. But consider it sounds better than any kicker subs and every home audio sub I've ever heard. ( I have yet to have the privilege of "experiencing" a JL Gotham so don't go there! Also no LMS experience either.)